Display device using semiconductor light emitting device surrounded by conductive electrode and method for manufacturing the same

ABSTRACT

The present disclosure relates to a display device and a fabrication method thereof, and more particularly, to a display device using a semiconductor light emitting device. The display device includes a semiconductor light emitting device disposed on a substrate, and having a first conductive electrode disposed on an upper edge of the semiconductor light emitting device, and a second conductive electrode disposed on an upper central portion of the semiconductor light emitting device and surrounded by the first conductive electrode, a passivation layer disposed to cover a part of an upper surface of the semiconductor light emitting device, a first wiring electrode electrically connected to the first conductive electrode and a second wiring electrode electrically connected to the second conductive electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.16/415,541, filed on May 17, 2019 (now U.S. Pat. No. 10,573,626, issuedon Feb. 25, 2020), which claims the benefit of priority to KoreanApplication No. 10-2018-0128470, filed on Oct. 25, 2018, all of theseapplications are hereby expressly incorporated by reference into thepresent application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a display device and a fabricationmethod thereof, and more particularly, to a display device using asemiconductor light emitting device.

2. Description of the Related Art

In recent years, liquid crystal displays (LCDs), organic light emittingdiode (OLED) displays, and micro LED displays have been competing toimplement a large-area display in the field of display technology.

However, there exist problems such as a slow response time, lowefficiency of light generated by backlight in case of LCDs, and thereexist drawbacks such as a short life span, reduced yield as well as lowefficiency in case of OLEDs.

On the contrary, when semiconductor light emitting devices (micro LED(μLED)) having a diameter or a cross sectional area of 100 microns orless are used in a display, the display can provide a very highefficiency because it does not absorb light using a polarizing plate orthe like. However, since a large-sized display requires millions ofsemiconductor light emitting devices, it has difficulty in transferringthe devices compared to other technologies.

Technologies currently in development for transfer processes includepick & place, laser lift-off (LLO), self-assembly, or the like. Amongthem, the self-assembly method, which is a method in which thesemiconductor light emitting device locates themselves in a fluid, isthe most advantageous method for realizing a large-sized display device.

In recent years, U.S. Pat. No. 9,825,202 proposed a micro LED structuresuitable for self-assembly, but there is not yet research ontechnologies for fabricating a display through self-assembly of microLEDs. Accordingly, the present disclosure proposes a new type of displaydevice in which micro LEDs can be self-assembled and a fabricationmethod thereof.

SUMMARY OF THE INVENTION

An object of the present disclosure is to provide a fabrication methodand structure for reducing a process error in fabricating a displaydevice including semiconductor light emitting devices.

Another object of the present disclosure is to provide a fabricationmethod and structure for reducing the number of processes required infabricating a display device including semiconductor light emittingdevices.

The present disclosure can provide a display device, including asubstrate, semiconductor light emitting device having a first conductiveelectrode disposed on the substrate and formed annularly on an upperedge thereof and a second conductive electrode formed on an uppercentral portion thereof and surrounded by the first conductiveelectrode, a passivation layer formed to cover a part of an uppersurface of the semiconductor light emitting device, a first wiringelectrode electrically connected to the first conductive electrode, anda second wiring electrode extended from the upper edge of thesemiconductor light emitting device to the upper central portion of thesemiconductor light emitting device and electrically connected to thesecond conductive electrode, wherein a part of the second wiringelectrode overlaps with a part of the first conductive electrode withthe passivation layer interposed therebetween.

According to an embodiment, the passivation layer can be extended from aside surface of the semiconductor light emitting device in a widthdirection of the semiconductor light emitting device, and formed tocover parts of the first and second conductive electrodes.

According to an embodiment, the passivation layer can be formed to covera remaining portion of the upper surface of the semiconductor lightemitting device excluding a portion of the first and second conductiveelectrodes electrically connected to the first and second wiringelectrodes.

According to an embodiment, the semiconductor light emitting device canbe formed symmetrically with respect to a widthwise center line thereof.

According to an embodiment, the first and second conductive electrodescan be disposed with a height difference with respect to a thicknessdirection of the semiconductor light emitting device.

According to an embodiment, the semiconductor light emitting device caninclude a first conductive semiconductor layer disposed below the firstconductive electrode, a second conductive semiconductor layer disposedbelow the second conductive electrode, and an active layer formedbetween the first and second conductive semiconductor layers.

According to an embodiment, the active layer can be formed to overlapwith the second conductive electrode disposed at a central portion ofthe semiconductor light emitting device.

According to an embodiment, the active layer can be formed in an annularshape to overlap with the first conductive electrode.

In addition, the present disclosure can provide a fabrication method ofa display device, and the method can include fabricating a plurality ofsemiconductor light emitting devices each having a first conductiveelectrode formed annularly on an upper edge thereof and a secondconductive electrode formed at an upper central portion of thesemiconductor light emitting device and surrounded by the firstconductive electrode on a wafer, forming a passivation layer that coversan upper surface of the semiconductor light emitting device,transferring a substrate to an assembly position, and placing thesemiconductor light emitting devices into a fluid chamber, guiding themovement of the semiconductor light emitting devices in the fluidchamber to assemble the semiconductor light emitting devices at presetpositions of the substrate, etching parts of the passivation layeroverlapping with the first and second conductive electrodes to exposeportions of the first and second conductive electrodes, and connectingfirst and second wiring electrodes to the first and the secondconductive electrodes.

According to an embodiment, forming the passivation layer can be carriedout to cover an entire upper surface of the semiconductor light emittingdevice.

According to an embodiment, etching the passivation layer can be carriedout subsequent to assembling the plurality of semiconductor lightemitting devices at the preset positions of the substrate.

According to an embodiment, part of the second wiring electrode can bedisposed to overlap with a part of the first conductive electrode withthe passivation layer interposed therebetween.

According to the present disclosure, it is not required to perform theprocess of exposing conductive electrodes of semiconductor lightemitting devices to the outside in the fabrication of the semiconductorlight emitting devices. As a result, the number of processes is reduced,and the process error is reduced. Moreover, the size of thesemiconductor light emitting device can be reduced due to the reductionin the process error.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a view illustrating a display device using a semiconductorlight emitting device according to an embodiment of the presentdisclosure.

FIG. 2 is a partially enlarged view showing a portion “A” of the displaydevice in FIG. 1.

FIG. 3 is an enlarged view showing a semiconductor light emitting devicein FIG. 2.

FIG. 4 is an enlarged view showing another embodiment of thesemiconductor light emitting device in FIG. 2.

FIGS. 5A through 5G are views for explaining a new process offabricating the foregoing semiconductor light emitting device.

FIG. 6 is a view showing an example of a self-assembly device ofsemiconductor light emitting devices according to the presentdisclosure.

FIG. 7 is a block diagram showing the self-assembly device in FIG. 6.

FIGS. 8A through 8G are views showing a process of self-assemblingsemiconductor light emitting devices using the self-assembly device inFIG. 6.

FIGS. 9A through 9C are views showing a process of fabricating a displaydevice after self-assembling semiconductor light emitting devices on awiring substrate using the self-assembly device in FIG. 6.

FIG. 10A is a plan view showing a wiring substrate prior to transferringsemiconductor light emitting devices.

FIG. 10B is a plan view showing a wiring substrate subsequent totransferring semiconductor light emitting devices.

FIGS. 11A through 16 are views showing various modified embodiments of adisplay device according to the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, the embodiments disclosed herein will be described indetail with reference to the accompanying drawings, and the same orsimilar elements are designated with the same numeral referencesregardless of the numerals in the drawings and their redundantdescription will be omitted. A suffix “module” and “unit” used forconstituent elements disclosed in the following description is merelyintended for easy description of the specification, and the suffixitself does not give any special meaning or function. In describing thepresent disclosure, if a detailed explanation for a related knownfunction or construction is considered to unnecessarily divert the gistof the present disclosure, such explanation has been omitted but wouldbe understood by those skilled in the art. Also, it should be noted thatthe accompanying drawings are merely illustrated to easily explain theconcept of the invention, and therefore, they should not be construed tolimit the technological concept disclosed herein by the accompanyingdrawings.

Furthermore, it will be understood that when an element such as a layer,region or substrate is referred to as being “on” another element, it canbe directly on the another element or an intermediate element can alsobe interposed therebetween.

A display device disclosed herein can include a portable phone, a smartphone, a laptop computer, a digital broadcast terminal, a personaldigital assistant (PDA), a portable multimedia player (PMP), anavigation, a slate PC, a tablet PC, an ultrabook, a digital TV, adigital signage, a head-mounted display (HMD), a desktop computer, andthe like. However, it would be easily understood by those skilled in theart that a configuration disclosed herein can be applicable to anydisplayable device even though it is a new product type which will bedeveloped later.

FIG. 1 is a view showing a display device using a semiconductor lightemitting device according to an embodiment of the present disclosure,and FIG. 2 is a partially enlarged view showing a portion “A” of thedisplay device in FIG. 1, and FIG. 3 is an enlarged view showing asemiconductor light emitting device in FIG. 2, and FIG. 4 is an enlargedview showing another embodiment of the semiconductor light emittingdevice in FIG. 2.

According to the illustration, information processed in the controllerof the display device 100 can be displayed on a display module 101. Acase in the form of a closed loop surrounding an edge of the displaymodule can form a bezel of the display device.

The display module 101 can include a panel on which an image isdisplayed, and the panel can include micro-sized semiconductor lightemitting devices 150 and a wiring substrate 110 on which thesemiconductor light emitting devices 150 are mounted.

Wiring lines can be formed on the wiring substrate 110, and connected toan n-type electrode 152 and a p-type electrode 156 of the semiconductorlight emitting device 150. Through this, the semiconductor lightemitting device 150 can be provided on the wiring substrate 110 as aself-emitting individual pixel.

An image displayed on the panel is visual information, and implementedby independently controlling the light emission of a sub-pixel arrangedin a matrix form through the wiring lines.

According to the present invention, a micro LED (Light Emitting Diode)is illustrated as one type of the semiconductor light emitting device150 that converts current into light. The micro LED can be a lightemitting diode formed with a small size of 100 microns or less. Thesemiconductor light emitting device 150 can be provided in blue, red,and green light emitting regions, respectively, to implement a sub-pixelby a combination of the light emitting regions. In other words, thesub-pixel denotes a minimum unit for implementing a single color, and atleast three micro LEDs can be provided in the sub-pixel.

More specifically, referring to FIG. 3, the semiconductor light emittingdevice 150 can be a vertical structure.

For example, the semiconductor light emitting devices 150 can beimplemented with a high-power light emitting device that emits variouslights including blue in which gallium nitride (GaN) is mostly used, andindium (In) and or aluminum (Al) are added thereto.

The vertical semiconductor light emitting device can include a p-typeelectrode 156, a p-type semiconductor layer 155 formed with the p-typeelectrode 156, an active layer 154 formed on the p-type semiconductorlayer 155, an n-type semiconductor layer 153 formed on the active layer154, and an n-type electrode 152 formed on the n-type semiconductorlayer 153. In this case, the p-type electrode 156 located at the bottomcan be electrically connected to a p-electrode of the wiring substrate,and the n-type electrode 152 located at the top can be electricallyconnected to an n-electrode at an upper side of the semiconductor lightemitting device. The electrodes can be disposed in the upward/downwarddirection in the vertical semiconductor light emitting device 150,thereby providing a great advantage capable of reducing the chip size.

For another example, referring to FIG. 4, the semiconductor lightemitting device can be a flip chip type semiconductor light emittingdevice.

For such an example, the semiconductor light emitting device 250 caninclude a p-type electrode 256, a p-type semiconductor layer 255 formedwith the p-type electrode 256, an active layer 254 formed on the p-typesemiconductor layer 255, an n-type semiconductor layer 253 formed on theactive layer 254, and an n-type electrode 252 disposed to be separatedfrom the p-type electrode 256 in the horizontal direction on the n-typesemiconductor layer 253. In this case, both the p-type electrode 256 andthe n-type electrode 252 can be electrically connected to thep-electrode and the n-electrode of the wiring substrate at the bottom ofthe semiconductor light emitting device.

The vertical semiconductor light emitting device and the horizontalsemiconductor light emitting device can be a green semiconductor lightemitting device, a blue semiconductor light emitting device, or a redsemiconductor light emitting device, respectively. The greensemiconductor light emitting device and the blue semiconductor lightemitting device can be mostly formed of gallium nitride (GaN), andindium (In) and/or aluminum (Al) can be added thereto to implement ahigh-power light emitting device that emits green or blue light. Forsuch an example, the semiconductor light emitting device can be agallium nitride thin-film formed in various layers such as n-Gan, p-Gan,AlGaN, and InGa, and specifically, the p-type semiconductor layer can bep-type GaN, and the n-type semiconductor layer can be N-type GaN.However, in case of the red semiconductor light emitting device, thep-type semiconductor layer can be p-type GaAs and the n-typesemiconductor layer can be n-type GaAs.

In addition, a p-electrode side in the p-type semiconductor layer can bep-type GaN doped with Mg, and an n-electrode side in the n-typesemiconductor layer can be n-type GaN doped with Si. In this case, theabove-described semiconductor light emitting devices can besemiconductor light emitting devices without an active layer.

On the other hand, referring to FIGS. 1 through 4, since the lightemitting diode is very small, the display panel can be arranged withself-emitting sub-pixels arranged at fine pitch, thereby implementing ahigh-quality display device.

In a display device using the semiconductor light emitting device of thepresent disclosure described above, a semiconductor light emittingdevice grown on a wafer and formed through mesa and isolation is used asan individual pixel. In this case, the micro-sized semiconductor lightemitting device 150 must be transferred to a wafer at a predeterminedposition on the substrate of the display panel. Pick and place is usedfor the transfer technology, but the success rate is low and a lot oftime is required. For another example, there is a technology oftransferring a plurality of devices at one time using a stamp or a roll,but the yield is limited and not suitable for a large screen display.The present disclosure proposes a new fabrication method of a displaydevice capable of solving the foregoing problems and a fabricationdevice using the same.

For this purpose, first, a new fabrication method of the display devicewill be described. FIGS. 5A through 5G are views for explaining a newprocess of fabricating the foregoing semiconductor light emittingdevice.

In this specification, a display device using a passive matrix (PM)semiconductor light emitting device is illustrated. However, an exampledescribed below can also be applicable to an active matrix (AM) typesemiconductor light emitting device. In addition, a method using ahorizontal semiconductor light emitting device is illustrated, but it isalso applicable to a method of self-assembling a vertical semiconductorlight emitting device.

First, according to a manufacturing method, a first conductivesemiconductor layer 153, an active layer 154, and a second conductivesemiconductor layer 155 are respectively grown on a growth substrate159.

When the first conductive semiconductor layer 153 is grown, next, theactive layer 154 is grown on the first conductive semiconductor layer153, and then the second conductive semiconductor layer 155 is grown onthe active layer 154. As described above, when the first conductivesemiconductor layer 153, the active layer 154 and the second conductivesemiconductor layer 155 are sequentially grown, the first conductivesemiconductor layer 153, the active layer 154, and the second conductivesemiconductor layer 155 form a layer structure as illustrated in FIG.5A.

In this case, the first conductive semiconductor layer 153 can be ann-type semiconductor layer, and the second conductive semiconductorlayer 155 can be a p-type semiconductor layer. However, the presentdisclosure is not limited thereto, and the first conductive type can bep-type and the second conductive type can be n-type.

In addition, the present embodiment illustrates a case where the activelayer is present, but it is also possible to adopt a structure in whichthe active layer is not present as described above. For such an example,the p-type semiconductor layer can be p-type GaN doped with Mg, and ann-electrode side in the n-type semiconductor layer can be n-type GaNdoped with Si.

The growth substrate 159 (wafer) can be formed of any one of materialshaving light transmission properties, for example, sapphire (Al2O3),GaN, ZnO, and AlO, but is not limited thereto. Furthermore, the growthsubstrate 159 can be formed of a carrier wafer, which is a materialsuitable for semiconductor material growth. The growth substrate (W) canbe formed of a material having an excellent thermal conductivity, andfor example, a SiC substrate having a higher thermal conductivity than asapphire (Al2O3) substrate or a SiC substrate including at least one ofSi, GaAs, GaP, InP and Ga2O3 can be used.

Next, at least part of the first conductive semiconductor layer 153, theactive layer 154 and the second conductive semiconductor layer 155 isremoved to form a plurality of epi chips of the semiconductor lightemitting devices (FIG. 5B).

More specifically, isolation is carried out so that a plurality of lightemitting devices form an array with epi chips. In other words, the firstconductive semiconductor layer 153, the active layer 154, and the secondconductive semiconductor layer 155 are etched in a vertical direction toform a plurality of semiconductor light emitting devices (FIG. 5C).

At this stage, the active layer 154 and the second conductivesemiconductor layer 155 can be partially removed in a vertical directionto perform a mesa process in which the first conductive semiconductorlayer 153 is exposed to the outside, and then isolation in which thefirst conductive semiconductor layer is etched to form a plurality ofsemiconductor light emitting device arrays. In this case, thesemiconductor light emitting device can be isolated to a circular sizeof 100 μm or less in diameter.

Next, a second conductive electrode 156 (or a p-type electrode) isformed on one surface of the second conductive semiconductor layer 155(FIG. 5D). The second conductive electrode 156 can be formed by adeposition process such as sputtering, but the present disclosure is notnecessarily limited thereto. However, when the first conductivesemiconductor layer and the second conductive semiconductor layer are ann-type semiconductor layer and a p-type semiconductor layer,respectively, the second conductive electrode 156 can also be an n-typeelectrode.

Next, a passivation layer 170 covering side and upper surfaces of thesemiconductor light emitting device is formed (FIG. 5E).

Here, the passivation layer can be a polymer type or an inorganic type(e.g., SiO₂), but is not limited thereto. Meanwhile, the passivationlayer 170 can be formed of the same material as a passivation layerformed on the side and upper surfaces of the semiconductor lightemitting device.

The passivation layer 170 is formed to cover the first conductivesemiconductor layer or the second conductive semiconductor layer 153,155 exposed to the outside, and formed to cover the first and secondconductive electrodes 152, 156 exposed to the outside. Accordingly, thepassivation layer 170 can be formed to cover an entire upper surface ofthe semiconductor light emitting device. However, the present disclosureis not limited thereto, and the passivation layer can be formed to coveronly part of an upper surface of the semiconductor light emittingdevice.

Then, the growth substrate 159 is removed to provide a plurality ofsemiconductor light emitting devices 250. For example, the growthsubstrate 159 can be removed using a laser lift-off (LLO) or chemicallift-off (CLO) method (FIG. 5F).

The passivation layer 170 is present on the upper and side surfaces ofthe semiconductor light emitting device that has been released throughthe above process. Then, the process of mounting the plurality ofsemiconductor light emitting devices 250 on the substrate in a chamberfilled with a fluid (FIG. 5G).

For example, the semiconductor light emitting devices 250 and thesubstrate are placed in a chamber filled with a fluid, and thesemiconductor light emitting devices 250 are assembled to the substrateby themselves using flow, gravity, surface tension, or the like.

In the present disclosure, the substrate can be a wiring substrate 261.In other words, the wiring substrate 261 is placed in the fluid chamberso that the semiconductor light emitting devices 250 are directlymounted on the wiring substrate 261.

Hereinafter, an embodiment for mounting the semiconductor light emittingdevices 250 on the wiring substrate 261 will be described in detail withreference to the accompanying drawings.

FIG. 6 is a view showing an example of a self-assembly device ofsemiconductor light emitting devices according to the present invention,and FIG. 7 is a block diagram showing the self-assembly device in FIG.6. Furthermore, FIGS. 8A through 8G are views showing a process ofself-assembling semiconductor light emitting devices using theself-assembly device in FIG. 6.

According to the illustration of FIGS. 6 and 7, a self-assembly device160 of the present disclosure can include a fluid chamber 162, a magnet163, and a location controller 164.

The fluid chamber 162 has a space for accommodating a plurality ofsemiconductor light emitting devices. The space can be filled with afluid, and the fluid can include water or the like as an assemblysolution. Accordingly, the fluid chamber 162 can be a water tank, andcan be configured with an open type. However, the present disclosure isnot limited thereto, and the fluid chamber 162 can be a closed type inwhich the space is formed with a closed space.

The substrate 261 can be disposed on the fluid chamber 162 such that anassembly surface on which the semiconductor light emitting devices 250are assembled faces downward. For example, the substrate 261 can betransferred to an assembly position by a transfer unit, and the transferunit can include a stage 165 on which the substrate is mounted. Thestage 165 is positioned by the controller, and the substrate 261 can betransferred to the assembly position through the stage 165.

At this time, the assembly surface of the substrate 261 faces the bottomof the fluid chamber 162 at the assembly position. According to theillustration, the assembly surface of the substrate 261 is disposed soas to be immersed in a fluid in the fluid chamber 162. Therefore, thesemiconductor light emitting devices 250 are moved to the assemblysurface in the fluid.

The substrate 261, which is an assembly substrate on which an electricfield can be formed as well as a wiring substrate on which wiring linesare formed afterward, can include a base portion 261 a, a dielectriclayer 261 b and a plurality of electrodes 261 c, 261 d.

The base portion 261 a can be made of an insulating material, and theplurality of electrodes 261 c can be a thin or a thick film bi-planarelectrode patterned on one side of the base portion 261 a. The electrode261 c can be formed of, for example, a laminate of Ti/Cu/Ti, an Agpaste, ITO, and the like.

More specifically, the electrode 261 c can be a plurality of pairelectrodes disposed on the substrate and provided with a first electrode261 c and a second electrode 261 d that generate an electric field whenan electric current is supplied.

The dielectric layer 261 b is made of an inorganic material such asSiO₂, SiNx, SiON, Al₂O₃, TiO₂, HfO₂, or the like. Alternatively, thedielectric layer 261 b can be composed of a single layer or multiplelayers as an organic insulator. A thickness of the dielectric layer 261b can be several tens of nanometers to several micrometers.

Furthermore, the wiring substrate 261 according to the presentdisclosure includes a plurality of cells 261 d partitioned by partitionwalls.

For example, the wiring substrate 261 can be provided with cells 261 dthrough which the semiconductor light emitting devices 250 are insertedso that the semiconductor light emitting devices 250 can easily bemounted on the wiring substrate 261 Specifically, cells 261 d on whichthe semiconductor light emitting devices 250 are mounted are formed onthe wiring substrate 261 at positions where the semiconductor lightemitting devices 250 are aligned with the wiring electrodes. Thesemiconductor light emitting devices 250 are assembled into the cells261 d while moving in the fluid.

The cells 261 d are sequentially arranged along one direction, and thepartition walls 261 e constituting the cells 261 d are shared with theneighboring cells 261 d. In this case, the partition walls 261 e can bemade of a polymer material. Furthermore, the partition walls 261 e areprotruded from the base portion 261 a, and the cells 261 d can besequentially arranged along the one direction by the partition walls 261e. More specifically, the cells 261 d are sequentially arranged in rowand column directions, and can have a matrix structure.

As shown in the drawing, an inside of the cells 261 d has a groove foraccommodating the semiconductor light emitting device 250, and thegroove can be a space defined by the partition walls 261 e. The shape ofthe groove can be the same as or similar to that of the semiconductorlight emitting device. For example, when the semiconductor lightemitting device is in a rectangular shape, the groove can be arectangular shape. In addition, although not shown, when thesemiconductor light emitting device is circular, the grooves formed inthe cells can be formed in a circular shape. Moreover, each of the cellsis configured to accommodate a single semiconductor light emittingdevice. In other words, a single semiconductor light emitting device isaccommodated in a single cell.

On the other hand, according to the present disclosure, a material sameas that of the partition walls 261 e can be filled inside the cells 261d by a subsequent process. Accordingly, the partition walls 261 e can bemodified into a passivation layer surrounding the semiconductor lightemitting devices. This will be described later.

On the other hand, a plurality of electrodes can be disposed on thesubstrate, and have a first electrode and a second electrode thatgenerate an electric field when an electric current is supplied, and thefirst electrode and the second electrode can be referred to as a pairelectrode 261 c. In the present disclosure, a plurality of the pairelectrodes 261 c can be provided, and disposed at the bottom of each ofthe cells 261 d. The first electrode and the second electrode can beformed of electrode lines, and the plurality of electrode lines can beextended to neighboring cells.

The pair electrodes 261 c are disposed below the cells 261 d and appliedwith different polarities to generate an electric field in the cells 261d. In order to form the electric field, the dielectric layer can formthe bottom of the cells 261 d while the dielectric layer covers the pairelectrodes 261 c. In such a structure, when different polarities areapplied to the pair electrode 261 c from a lower side of each cell 261d, an electric field can be formed, and the semiconductor light emittingdevice can be inserted into the cells 261 d by the electric field.

At the assembly position, the electrodes of the substrate 261 areelectrically connected to the power supply unit 171. The power supplyunit 171 applies power to the plurality of electrodes to generate theelectric field.

According to the illustration, the self-assembly device can include amagnet 163 for applying a magnetic force to the semiconductor lightemitting devices. The magnet 163 is spaced apart from the fluid chamber162 to apply a magnetic force to the semiconductor light emittingdevices 250. The magnet 163 can be disposed to face an opposite side ofthe assembly surface of the substrate 261, and the location of themagnet is controlled by the location controller 164 connected to themagnet 163. The semiconductor light emitting device 250 can have amagnetic body so as to move in the fluid by the magnetic field of themagnet 163.

Referring to FIGS. 6 and 7, more specifically, the self-assembly devicecan include a magnet handler that can be automatically or manually movedin the x, y, and z axes on the top of the fluid chamber or include amotor capable of rotating the magnet 163. The magnet handler and themotor can constitute the location controller 164. Through this, themagnet 163 rotates in a horizontal direction, a clockwise direction, ora counterclockwise direction with respect to the substrate 161.

On the other hand, a light transmitting bottom plate 166 can be formedin the fluid chamber 162, and the semiconductor light emitting devicescan be disposed between the bottom plate 166 and the substrate 161. Animage sensor 167 can be positioned to view the bottom plate 166 so as tomonitor an inside of the fluid chamber 162 through the bottom plate 166.The image sensor 167 is controlled by the controller 172, and caninclude an inverted type lens, a CCD, and the like to observe theassembly surface of the substrate 261.

The self-assembling apparatus described above is configured to use acombination of a magnetic field and an electric field, and using thosefields, the semiconductor light emitting devices can be placed at presetpositions of the substrate by an electric field in the process of beingmoved by a location change of the magnet. Such a new fabrication methodcan be a detailed example of the self-assembly method described abovewith reference to FIG. 5E. Hereinafter, an assembly process using theself-assembly device described above will be described in more detail.

First, a plurality of semiconductor light emitting devices 250 areformed through the process described with reference to FIGS. 5A through5G. In this case, a magnetic body can be deposited on the semiconductorlight emitting device in the process of forming the second conductiveelectrode in FIG. 5C. The magnetic body can control the movement of thesemiconductor light emitting device by the magnet 163.

Next, the substrate 261 is transferred to the assembly position, and thesemiconductor light emitting devices 250 are put into the fluid chamber162 (FIG. 8A).

As described above, the assembly position of the substrate 261 is aposition at which the assembly surface on which the semiconductor lightemitting devices 250 of the substrate 261 are assembled is disposed in adownward direction in the fluid chamber 162.

In this case, some of the semiconductor light emitting devices 250 cansink to the bottom of the fluid chamber 162 and some can float in thefluid. When the light transmitting bottom plate 166 is provided in thefluid chamber 162, some of the semiconductor light-emitting devices 250can sink to the bottom plate 166.

Next, a magnetic force is applied to the semiconductor light emittingdevices 250 so that the semiconductor light emitting devices 250 floatin the fluid chamber 162 in a vertical direction (FIG. 8B).

When the magnet 163 of the self-assembly device moves from its originalposition to an opposite side of the assembly surface of the substrate261, the semiconductor light emitting devices 250 float in the fluidtoward the substrate 261. The original position can be a position awayfrom the fluid chamber 162. For another example, the magnet 163 can becomposed of an electromagnet. In this case, electricity is supplied tothe electromagnet to generate an initial magnetic force.

Meanwhile, in this example, a separation distance between the assemblysurface of the substrate 261 and the semiconductor light emittingdevices 250 can be controlled by adjusting the magnitude of the magneticforce. For example, the separation distance is controlled using theweight, buoyancy, and magnetic force of the semiconductor light emittingdevices 250. The separation distance can be several millimeters to tensof micrometers from the outermost edge of the substrate.

Next, a magnetic force is applied to the semiconductor light emittingdevices 250 so that the semiconductor light emitting devices 250 move inone direction in the fluid chamber 162. For example, the magnet 163moves in a horizontal direction, a clockwise direction or acounterclockwise direction with respect to the substrate (FIG. 8C). Inthis case, the semiconductor light emitting devices 250 move in adirection parallel to the substrate 161 at a position spaced apart fromthe substrate 161 by the magnetic force.

Next, the process of applying an electric field to guide thesemiconductor light emitting devices 250 to preset positions of thesubstrate 161 so as to allow the semiconductor light emitting devices250 to be placed at the preset positions during the movement of thesemiconductor light emitting devices 250 is carried out (FIG. 8D). Thesemiconductor light emitting devices 250 move in a directionperpendicular to the substrate 261 by the electric field to be placed onpreset positions while moving along a direction parallel to thesubstrate 161.

The plurality of semiconductor light emitting devices are guided topreset positions of the substrate by an electric field and a magneticfield.

More specifically, electric power is supplied to a pair electrode, thatis, a bi-planar electrode of the substrate 261 to generate an electricfield, and assembly is carried out only at preset positions. In otherwords, the semiconductor light emitting devices 250 are assembled to theassembly position of the substrate 261 using a selectively generatedelectric field. For this purpose, the substrate 261 can include cells inwhich the semiconductor light emitting devices 250 are inserted.

At this time, the magnetic body of the semiconductor light emittingdevices 250 serves as a post for upper and lower division. Specifically,when a surface having the magnetic body is inserted into the cell in adirection toward the pair electrode 261 c, the semiconductor lightemitting device is unable to be placed on the bottom of the cell (anouter surface of the dielectric layer) by the magnetic body.

On the other hand, the semiconductor light emitting devices 250 can beguided to the preset positions, then the magnet 163 can move in adirection away from the substrate 261 such that the semiconductor lightemitting devices 250 remaining in the fluid chambers 162 fall to thebottom of the fluid chambers 162, (FIG. 8E). For another example, ifpower supply is stopped when the magnet 163 is an electromagnet, thenthe semiconductor light emitting devices 250 remaining in the fluidchamber 162 fall to the bottom of the fluid chamber 162.

Then, when the semiconductor light emitting devices 250 on the bottom ofthe fluid chamber 162 are collected, the collected semiconductor lightemitting devices 250 can be reused.

When the display device of the present disclosure uses bluesemiconductor light emitting devices, that is, when the semiconductorlight emitting devices are all blue semiconductor light emittingdevices, the blue semiconductor light emitting devices can be assembledinto all the cells of the substrate.

On the other hand, according to this example, each of the redsemiconductor light emitting device, the green semiconductor lightemitting device, and the blue semiconductor light emitting device can bearranged at a desired position. If the foregoing semiconductor lightemitting device 250 is a blue semiconductor light emitting device, theassembly process described with reference to FIGS. 8A through 8E cangenerate an electric field only in a cell corresponding to a blue pixelto assemble the blue semiconductor light emitting device at acorresponding position.

Then, the assembly process described with reference to 8A through 8E arecarried out using the green semiconductor light emitting device 250 aand the red semiconductor light emitting device 250 b, respectively(FIGS. 8F and 8G). However, since the wiring substrate 261 is alreadyloaded at the assembly position, the process of loading the substrateinto the assembly position can be omitted.

Then, the process of unloading the wiring substrate 261 is carried out,and the assembly process is completed.

The above-described self-assembly device and method are characterized inthat, in order to increase the assembly yield in a fluidic assembly,parts at a far distance are concentrated adjacent to a preset assemblysite using a magnetic field, and a separate electric field is applied tothe assembly site to selectively assemble the parts only in the assemblysite. At this time, the assembly substrate is placed on an upper portionof the water tank and the assembly surface faces downward, therebypreventing nonspecific coupling while minimizing the effect of gravitydue to the weight of parts. In other words, in order to increase thetransfer yield, the assembly substrate is placed on the top to minimizethe effect of a gravitational or frictional force, and preventnonspecific coupling.

Meanwhile, in order to minimize non-specific coupling of thesemiconductor light emitting device, the semiconductor light emittingdevice can have a structure symmetrically formed with respect to a widthdirection of the semiconductor light emitting device.

Furthermore, the blue semiconductor light emitting device, the greensemiconductor light emitting device, and the red semiconductor lightemitting device can be assembled at desired positions, respectively.

As described above, according to the present disclosure having theforegoing configuration, a large number of semiconductor light emittingdevices can be assembled at one time in a display device in whichindividual pixels are formed with semiconductor light emitting devices.

When the assembly process is completed as described above, a process offabricating a display device can be carried out. Hereinafter, afabrication process of such a display device will be described in detailwith reference to the drawings.

FIGS. 9A through 9C are views showing a process of fabricating a displaydevice after self-assembling semiconductor light emitting devices on awiring substrate using the self-assembly device in FIG. 6.

The movement of the semiconductor light emitting devices in the fluidchamber are guided, and the semiconductor light emitting devices areassembled at preset positions of the substrate by the foregoing process,and then the second conductive electrodes 252, 256 are exposed to theoutside while the semiconductor light emitting devices 250, 250 a, 250 bare assembled at the preset positions of the substrate 261.

To this end, the process of etching part of the passivation layeroverlapping with the first and second conductive electrodes 252, 256 iscarried out (FIG. 9A). In this process, the passivation layer 170 isetched only at a portion where the wiring electrodes and the first andsecond conductive electrodes are to be removed for electricalconnection. Therefore, a portion that is not connected to the wiringelectrode on the entire region of the passivation layer is not etched.In particular, in the etching process, the entire region of the firstand second conductive electrodes 252, 256 is not exposed to the outside,but only part of the first and second conductive electrodes 252, 256connected to the wiring electrode is exposed to the outside (FIG. 9B).

Then, the process of connecting the first and second wiring electrodesto the first and second conductive electrodes is carried out (FIG. 9C).In this process, the second wiring electrode is inevitably overlappedwith the first conductive electrode. Specifically, since the firstconductive electrode is disposed so as to surround the second conductiveelectrode, in order to electrically connect the second wiring electrodeto the second conductive electrode, the second wiring electrode isinevitably overlapped with the first conductive electrode.

However, since most of the passivation layer covering the firstconductive electrode is not removed in the etching process, part of thesecond wiring electrode can be disposed to overlap with part of thefirst conductive electrode with the passivation layer interposedtherebetween. The passivation layer prevents the first conductiveelectrode and the second wiring electrode from being electricallyconnected to each other.

According to the fabrication method described above, since thepassivation layer covering most of the semiconductor light emittingdevice is formed from the fabrication of the semiconductor lightemitting device, it is not required to form an additional passivationlayer subsequent to transferring the semiconductor light emittingdevice.

In addition, according to the present disclosure, it is not required toperform the process of exposing the conductive electrode of thesemiconductor light emitting device to the outside in the fabricationprocess of the semiconductor light emitting device. As a result, thenumber of processes is reduced, and the process error is reduced.Moreover, the size of the semiconductor light emitting device can bereduced due to the reduction in the process error.

Furthermore, when the processes of FIGS. 8A through 8G are carried outsubsequent to exposing part of the conductive electrode to the outsidein the fabrication process of the semiconductor light emitting device,positions where the conductive electrodes are exposed are different foreach semiconductor light emitting device. When the conductive electrodeis irregularly exposed to the outside, it is difficult to connect thewiring electrode to the conductive electrode. According to the presentdisclosure, since the conductive electrode is exposed to the outsidesubsequent to transferring the semiconductor light emitting device, theposition of the conductive electrode exposed to the outside becomesuniform. Through this, the present disclosure makes it possible toeasily form the wiring electrode subsequent to the transfer of thesemiconductor light emitting device.

Hereinafter, the structure of a display device formed through theprocesses described in FIGS. 9A to 9C will be described in more detail.

FIG. 10A is a plan view showing a wiring substrate prior to transferringsemiconductor light emitting devices, and FIG. 10B is a plan viewshowing a wiring substrate subsequent to transferring semiconductorlight emitting devices.

Referring to FIG. 10A, electrodes 261 c for forming an electric field inthe process described in FIGS. 8A through 8G, line electrodes 120, 140for supplying an external power source to the semiconductor lightemitting device, and holes to be placed at the designated positions canbe formed on the wiring substrate.

FIG. 10B shows a structure in which the semiconductor light emittingdevices 250 are placed on the wiring substrate and then the wiringelectrodes are formed thereon. Referring to the drawing, the firstconductive electrode and the second conductive electrode must beelectrically connected to different line electrodes. A first wiringelectrode 121 connected to a first line electrode 120 is electricallyconnected to the first conductive electrode 252, and a second wiringelectrode 141 connected to a second line electrode 140 is electricallyconnected to the second conductive electrode 256.

The display device fabricated through the process of FIGS. 9A through 9Chas the structure of FIG. 10B. Here, the structure of the display devicevaries depending on the structure of the semiconductor light emittingdevice.

FIGS. 11A through 12B are views showing various modified embodiments ofa display device according to the present invention.

Referring to FIGS. 11A through 12B, the first conductive electrode 352is formed in a ring shape on an upper edge of the semiconductor lightemitting device, and the second conductive electrode 356 is formed at anupper central portion of the semiconductor light emitting device.

On the other hand, the passivation layer 170 is disposed to cover partof the side and upper surfaces of the semiconductor light emittingdevice. Specifically, the passivation layer 170 is disposed to cover anupper surface of the semiconductor light emitting device except part ofthe first and second conductive electrodes 352, 356 connected to thefirst and second wiring electrodes 121, 141. Since the passivation layeris formed on the side and upper surfaces of the semiconductor lightemitting device through a single process, the passivation layer can beformed to extend from the side of the semiconductor light emittingdevice in a width direction of the semiconductor light emitting deviceand cover part of the first and second conductive electrodes.

On the other hand, the first and second wiring electrodes 121, 141 areextended from an edge of the semiconductor light emitting device in acentral direction of the semiconductor light emitting device such thatthe first wiring electrode 121 is electrically connected to the firstconductive electrode 352, and the second wiring electrode 141 iselectrically connected to the second conductive electrode. Accordingly,the second wiring electrode 141 overlaps with the first conductiveelectrode with the passivation layer 170 interposed therebetween.

On the other hand, the first and second conductive electrodes can bedisposed with a height difference with respect to a thickness directionof the semiconductor light emitting device.

First, referring to FIGS. 11A and 11B, an embodiment in which the secondconductive electrode is formed at a higher position than the firstconductive electrode will be described. FIG. 11B is a cross-sectionalview taken along line A-A in FIG. 11A.

The semiconductor light emitting device includes a first conductivesemiconductor layer 353 disposed below the first conductive electrode352, a second conductive semiconductor layer 355 disposed below thesecond conductive electrode 356, and an active layer 354 disposedbetween the first and second conductive semiconductor layers 353, 355.

Referring to FIG. 11B, the second conductive electrode 356 can bedisposed at a position higher than the first conductive electrode 352.The active layer 354 is disposed to overlap with the second conductiveelectrode 356 disposed at a central portion of the semiconductor lightemitting device. Since light is emitted from the active layer 354, lightis emitted from the central portion of the semiconductor light emittingdevice in the structure shown in FIGS. 11A and 11B.

Next, referring to FIGS. 12A and 12B, an embodiment in which the firstconductive electrode is formed at a higher position than the secondconductive electrode will be described. FIG. 12B is a cross-sectionalview taken along line B-B in FIG. 12A.

The semiconductor light emitting device includes a first conductivesemiconductor layer 353 disposed below the first conductive electrode352, a second conductive semiconductor layer 355 disposed below thesecond conductive electrode 356, and an active layer 354 disposedbetween the first and second conductive semiconductor layers 353, 355.

Referring to FIG. 12B, the first conductive electrode 352 can bedisposed at a position higher than the second conductive electrode 356.The active layer 354 is formed in a ring shape to overlap with the firstconductive electrode 352. In the structure shown in FIGS. 12A and 12B, alight emitting surface is formed in a ring shape.

On the other hand, a recess portion can be formed on the first andsecond conductive semiconductor layers, and the first and secondconductive electrodes can be disposed in the recess portion.

In one embodiment, referring to FIGS. 13A and 13B, a recess portion canbe formed on the second conductive semiconductor layer 455, and a secondconductive electrode 456 can be disposed in the recess portion. Thestructure described above can reduce a height difference between theconductive semiconductor layer and the conductive electrode so that thepassivation layer 170 can be uniformly formed on an upper surface of thesemiconductor light emitting device 450 a, and afterwards the wiringelectrode can be uniformly formed on an upper surface of thesemiconductor light emitting device. The semiconductor light emittingdevice 450 a includes a first conductive semiconductor layer 453disposed below the first conductive electrode 452, a second conductivesemiconductor layer 455 disposed below the second conductive electrode456, and an active layer 454 disposed between the first and secondconductive semiconductor layers 453, 455.

On the other hand, the shape of the semiconductor light emitting deviceaccording to the present disclosure is not limited to a circular shape.

FIGS. 14A and 14B are views showing a different height differencebetween the conductive semiconductor layer and the conductive electrodeso that the passivation layer can be uniformly formed on an uppersurface of the semiconductor light emitting device 450 b, and afterwardsthe wiring electrode can be uniformly formed on an upper surface of thesemiconductor light emitting device.

FIGS. 15A and 15B are views showing an area of second conductiveelectrode 456 of the semiconductor light emitting device 450 b beingformed smaller than an upper surface of the second conductivesemiconductor layer 455 so that a portion of the second conductivesemiconductor layer 455 is present at the upper surface thereof tocontact the passivation layer 170.

FIG. 16 are views showing shapes of semiconductor light emitting deviceincluded in a display device according to the present disclosure.

In order to minimize non-specific coupling of the semiconductor lightemitting device in the self-assembly process described in FIGS. 8Athrough 8G, the present disclosure uses a semiconductor light emittingdevice having symmetry. Specifically, the semiconductor light emittingdevice included in the display device according to the presentdisclosure can be formed symmetrically with respect to a widthwisecenter line of the semiconductor light emitting device.

According to an embodiment, the semiconductor light emitting device canhave an equilateral triangle shape 550 a, as shown in (a) of FIG. 16, asquare shape 550 b, as shown in (b) of FIG. 16, and a circular shape 550c, as shown in (c) of FIG. 16. Although the shape of semiconductor lightemitting device and the shapes of the conductive semiconductor layersand the conductive electrodes correspond in FIG. 16, such is notrequired, and the shape of semiconductor light emitting device can bedifferent from the shapes of the conductive semiconductor layers and theconductive electrodes.

When a display device including semiconductor light emitting devicesthat emit light of different colors through self-assembly isimplemented, the possibility of occurrence of nonspecific couplingincreases as compared with a display device including one type ofsemiconductor light emitting devices.

The present disclosure can minimize the possibility of nonspecificcoupling by implementing a different shape of the semiconductor lightemitting device for each color of light emitted from the semiconductorlight emitting device.

According to an embodiment, the semiconductor light emitting device thatemits red light can be implemented as shown in (a) in FIG. 16, and thesemiconductor light emitting device that emits green light as shown in(b) in FIG. 16, and the semiconductor light emitting device that emitsblue light as shown in (c) in FIG. 16. On the other hand, differentshapes can be associated with different color lights.

A partition wall having a shape corresponding to the red, green, andblue semiconductor light emitting devices, respectively, can be formedon the substrate. During self-assembly, any one of the red, green, andblue semiconductor light emitting devices can be placed on only betweenthe partition walls corresponding thereto. Through this, light emittingdevices with different colors can be placed only at designated positionsduring self-assembly.

In embodiments, the first wiring electrode and the second wiringelectrode can be formed perpendicularly to each other. Also, the shapeof the first conductive electrode can be different from the shape of thesecond conductive electrode. Additionally, a thickness of thepassivation layer can be different from thicknesses of the first andsecond wiring electrodes.

According to the process and device of the present disclosure describedabove, a large number of semiconductor light emitting devices can bepixelated on a wafer having a small size, and then directly transferredonto a large-area substrate. Through this, it can be possible tofabricate a large-area display device at a low cost.

What is the claimed is:
 1. A display device, comprising: a semiconductorlight emitting device disposed on a substrate, and having a firstconductive electrode disposed on an upper edge of the semiconductorlight emitting device, and a second conductive electrode disposed on anupper central portion of the semiconductor light emitting device andsurrounded by the first conductive electrode; a passivation layerdisposed to cover a part of an upper surface of the semiconductor lightemitting device; a first wiring electrode electrically connected to thefirst conductive electrode; and a second wiring electrode electricallyconnected to the second conductive electrode, wherein a part of thesecond wiring electrode overlaps with a part of the first conductiveelectrode with the passivation layer interposed therebetween, andwherein the first conductive electrode is disposed at a position higherthan that of the second conductive electrode in a thickness direction ofthe semiconductor light emitting device.
 2. The display device of claim1, wherein the passivation layer is extended from a side surface of thesemiconductor light emitting device in a width direction of thesemiconductor light emitting device, and disposed to cover portions ofthe first and second conductive electrodes.
 3. The display device ofclaim 2, wherein the passivation layer is disposed to cover a remainingportion of the upper surface of the semiconductor light emitting deviceexcluding remaining portions of the first and second conductiveelectrodes respectively connected to the first and second wiringelectrodes.
 4. The display device of claim 1, wherein the semiconductorlight emitting device is formed symmetrically with respect to awidthwise center line thereof.
 5. The display device of claim 1, whereinthe second conductive electrode is disposed in a recessed portion of thesemiconductor light emitting device.
 6. The display device of claim 1,wherein the semiconductor light emitting device further comprises: afirst conductive type semiconductor layer disposed below the firstconductive electrode; a second conductive type semiconductor layerdisposed below the second conductive type electrode; and an active layerdisposed between the first and second conductive type semiconductorlayers.
 7. The display device of claim 6, wherein a height of the firstsemiconductor layer is greater than a height of the second conductiveelectrode.
 8. The display device of claim 6, wherein a height of thesecond conductive electrode is greater than a height of the activelayer.
 9. The display device of claim 6, wherein the active layer isdisposed to overlap with the second conductive electrode disposed at theupper central portion of the semiconductor light emitting device. 10.The display device of claim 6, wherein the active layer is formed in anannular shape to overlap with the first conductive electrode.
 11. Thedisplay device of claim 1, where the first wiring electrode and thesecond wiring electrode are disposed perpendicularly to each other. 12.The display device of claim 1, wherein a shape of the semiconductorlight emitting device is one of a triangle, a rectangle and a circle.13. The display device of claim 1, wherein a shape of the firstconductive electrode is different from a shape of the second conductiveelectrode.
 14. The display device of claim 1, wherein a thickness of thepassivation layer is different from thicknesses of the first and secondwiring electrodes.
 15. The display device of claim 1, wherein thepassivation layer is further formed to cover a side surface of thesemiconductor light emitting device.
 16. A display device, comprising: asubstrate; a semiconductor light emitting device disposed on thesubstrate, and including a first conductive type semiconductor layer, asecond conductive type semiconductor layer, an active layer disposedbetween the first and second conductive type semiconductor layers, afirst conductive electrode electrically connected to the firstconductive type semiconductor layer, and a second conductive electrodeconnected to the second conductive semiconductor layer; a first wiringelectrode electrically connected to the first conductive electrode; anda second wiring electrode electrically connected to the secondconductive electrode, wherein the second conductive electrode issurrounded by the first conductive electrode, and wherein the secondconductive electrode is disposed at a position higher than that of thefirst conductive electrode in a thickness direction of the semiconductorlight emitting device.
 17. The display device of claim 16, wherein thefirst conductive electrode is disposed on an edge of the semiconductorlight emitting device, and the second conductive electrode is disposedon a central portion of the semiconductor light emitting device.
 18. Thedisplay device of claim 16, wherein the first conductive electrode isdisposed at a position higher than that of the second conductiveelectrode in a thickness direction of the semiconductor light emittingdevice.
 19. A display device, comprising: a substrate; a semiconductorlight emitting device disposed on the substrate, and including a firstconductive type semiconductor layer, a second conductive typesemiconductor layer, an active layer disposed between the first andsecond conductive type semiconductor layers, a first conductiveelectrode electrically connected to the first conductive typesemiconductor layer, and a second conductive electrode connected to thesecond conductive semiconductor layer; a first wiring electrodeelectrically connected to the first conductive electrode; a secondwiring electrode electrically connected to the second conductiveelectrode; and a passivation layer disposed to cover a part of an uppersurface of the semiconductor light emitting device, wherein the secondconductive electrode is surrounded by the first conductive electrode,and wherein a part of the second wiring electrode overlaps with a partof the first conductive electrode with the passivation layer interposedtherebetween.